The present invention relates to a scroll type fluid displacement apparatus and, in particular, to a driving mechanism for an orbiting or movable scroll in the scroll type fluid displacement apparatus.
For example, U.S. Pat. No. 4,597,724 discloses a conventional scroll type fluid displacement apparatus including a fixed scroll, a movable scroll coupled to the fixed scroll, and a driving mechanism which is for causing a circular orbital motion of the movable scroll in dependence on a rotation of a main shaft. The orbital motion causes fluid pockets formed between the fixed scroll and the movable scroll to move and change their volumes to thereby compress introduced fluid. Accordingly, such a scroll type fluid displacement apparatus may be called a scroll type compressor.
In such a scroll type fluid displacement apparatus, it is necessary to inhibit the rotation of the movable scroll on its axis while performing the orbital motion. For this purpose, a rotation inhibiting mechanism is further provided in the fluid displacement apparatus.
As appreciated, when using a ball coupling mechanism or an Oldham's coupling mechanism as such a rotation inhibiting mechanism, the lower limit of a radius of the orbital motion of the movable scroll can not be regulated. Thus, for example, it is possible that a radius of the orbital motion of the movable scroll becomes so small upon start-up of the fluid displacement apparatus that the fluid displacement apparatus does not start the displacing operation.
Furthermore, when using the Oldham's coupling mechanism as such a rotation inhibiting mechanism, the upper limit of the orbital motion radius can not be regulated. Thus, upon mounting the movable scroll via the Oldham's coupling mechanism in an apparatus housing, a balance weight largely swings to interfere with the inner periphery of the apparatus housing.
Under the circumstances, a swing regulating mechanism is further required in the conventional fluid displacement apparatus for regulating a swing magnitude (orbital motion radius) of the movable scroll. In the conventional fluid displacement apparatus, the swing regulating mechanism is further utilized for facilitating assembling of the movable scroll.
On the other hand, provision of such a swing regulating mechanism causes the increase in manufacturing cost of the fluid displacement apparatus.